title: Long lasting persistence of Bacillus thuringiensis Subsp. israelensis (Bti) in mosquito natural habitats.
abstract: BACKGROUND
  The detrimental effects of chemical insecticides on the environment and human health have lead to the call for biological alternatives. Today, one of the most promising solutions is the use of spray formulations based on Bacillus thuringiensis subsp. israelensis (Bti) in insect control programs. As a result, the amounts of Bti spread in the environment are expected to increase worldwide, whilst the common belief that commercial Bti is easily cleared from the ecosystem has not yet been clearly established.
  
  
  RESULTS
  In this study, we aimed to determine the nature and origin of the high toxicity toward mosquito larvae found in decaying leaf litter collected in several natural mosquito breeding sites in the Rhône-Alpes region. From the toxic fraction of the leaf litter, we isolated B. cereus-like bacteria that were further characterized as B. thuringiensis subsp. israelensis using PCR amplification of specific toxin genes. Immunological analysis of these Bti strains showed that they belong to the H14 group. We finally used amplified length polymorphism (AFLP) markers to show that the strains isolated from the leaf litter were closely related to those present in the commercial insecticide used for field application, and differed from natural worldwide genotypes.
  
  
  CONCLUSIONS
  Our results raise the issue of the persistence, potential proliferation and environmental accumulation of human-spread Bti in natural mosquito habitats. Such Bti environmental persistence may lengthen the exposure time of insects to this bio-insecticide, thereby increasing the risk of resistance acquisition in target insects, and of a negative impact on non-target insects.
authors.affiliation: Floralis-UJF Filiale, Gières, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Tilquin
authors.forename: Margot
authors.initials: M
authors.lastname: Paris
authors.forename: Stéphane
authors.initials: S
authors.lastname: Reynaud
authors.forename: Laurence
authors.initials: L
authors.lastname: Despres
authors.forename: Patrick
authors.initials: P
authors.lastname: Ravanel
authors.forename: Roberto A
authors.initials: RA
authors.lastname: Geremia
authors.forename: Jérôme
authors.initials: J
authors.lastname: Gury
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000302:isolation & purification*; D009033:Culicidae / Q000382:microbiology*; D004269:DNA, Bacterial; D017753:Ecosystem; D005838:Genotype; D009032:Mosquito Control / Q000379:methods*; D018515:Plant Leaves / Q000382:microbiology; D016133:Polymerase Chain Reaction
chemical_list: D004269:DNA, Bacterial